The present invention relates to a shift mechanism of a motor vehicle transmission, and more particularly, to a shift mechanism having a shifting shaft which can be rotated to successively preselect the transmission gears and which can be longitudinally displaced to shift the transmission gears.
German Patent Document DE-OS 33 14 411 discloses a shift mechanism in which the transmission gears can be preselected by the longitudinal displacement of a reversing lever actuated by the shifting shaft, and can be shifted by rotation of the reversing lever. For the shifting of the transmission gears, the reversing lever displaces the shift rods on which respective shift forks are fastened which engage in synchronizer clutches of the transmission gears. For a five-speed transmission with a reverse gear, at least three shift rods are required which are longitudinally displaceably disposed in the transmission case.
It is an object of the present invention to lower the manufacturing costs of a shift mechanism and to reduce the friction during the preselecting and shifting of the transmission gears. This object has been achieved in accordance with the present invention by disposing a locking shaft in parallel to the shifting shaft so as to be lockable in the longitudinal direction, whereby the transmission gears that transmission gears that are not to be shifted are locked by the locking shaft.
If the transmission gears can be preselected and shifted directly by the rotation and longitudinal displacement of a shifting shaft, shift rods are thus not required. The saving of the shift rods, in addition to a lowering of the manufacturing costs, also leads to a reduction of the friction when the gear is operated. For the locking of the transmission gears that are not to be shifted, a locking shaft is used which is in parallel with the shift shaft and which is rotated along with the shift shaft during the preselection of the gears. The friction which occurs during the rotating movement is much lower than the sliding friction during the longitudinal displacement of shift rods.